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Your physiology is beautifully unique. I sound like John Mayer if he was a physical therapist. Our bodies are wonderlands, even if our glutes are unmaintained landfills.

The individual uniqueness of athletes creates a problem, though. How can we understand our physiology in the broader context of training theory when every variable is a bell curve across the population? General equations work if you're smack-dab in the middle of the bell curve thiccness, but can be actively wrong and counterproductive as you venture into the standard deviation hinterlands.

Consider the equation that many of you might have heard about heart rate: 180 beats per minute minus age = approximately aerobic threshold, or the intensity level that serves as a top-end barrier for easy/steady running that should encompass around 80% of your training volume. While that equation is generally useful, it can be actively useless for individuals, especially aging athletes who are highly trained and have a much higher aerobic threshold than the equation would predict.

For me, the equation caps my easy runs at 145 heart rate. My actual aerobic threshold is 152 beats per minute in running (and 150 beats per minute in biking). In practice, that's almost a one-minute-per-mile difference in output. Training from a general equation would prevent me from accruing benefits from steadier paces, and I'd probably be slower at everything.

raining zones from your watch can also be atrocious. In the last few months, I have helped a few hundred listeners of our podcast calculate their heart rate zones (our episode on heart rate zones is here). And a lesson I learned is that some of the watch brands use algorithms that are less accurate than U2 in Spanish class. Zone Uno, Zone Dos, Zone Tres, Zone Catorce, Zone Biblioteca, etc. Some of the watch zones are set so low that I have no idea what they could possibly be measuring. 

So today, let's look at one simple way to calculate your heart rate zones to help you calibrate your training intensity. Knowing your intensity ranges is helpful because it optimizes your metabolic fitness, allowing the body to burn more fat at higher outputs, while supporting mitochondrial proliferation and efficiency, allowing both higher and lower intensities to take less energy. Disclaimer: exercise physiology terminology is always subject to evolving debate, particularly on Twitter (the world's town square, if the square was also where the town put the raw sewage). Here is my favorite infographic ever on the overlap of these principles, from Fluid Athletics (follow them on Instagram here). 

What Are Heart Rate Zones?

We'll be using the traditional Five-Zone model, contrasted with the Three-Zone model used in most training research, but it helps to understand both and how they interact. Heart rate is best thought of as a proxy for lactate concentrations. To simplify it a ton, lactate is produced as our bodies use glucose to fuel ATP production during glycolysis. Lactate is a fuel source for cells, and it's accompanied by a hydrogen ion that changes muscle pH and contributes to fatigue. A 2018 review in Cell Metabolism described the lactate shuttle where the cells use lactate for energy. If this shuttling mechanism is overstressed, lactate levels and fatigue rise and exercise becomes less sustainable. A great overview by Dr. Howard Luks is here.

When lactate concentrations begin to rise, intensity switches from easy to moderate, an inflection point known as LT1, broadly overlapping with aerobic threshold where athletes go from primarily burning fat to primarily burning glycogen. And when lactate levels rise more steeply at higher intensities, intensity transitions from moderate to hard, an inflection point known as LT2, broadly overlapping with traditional lactate threshold (or critical velocity, depending on the method of calculation). That encompasses the 3-Zone model used in research:

Those zones are used in research to determine intensity distribution. While these breakdowns are gross approximations, it can help to put some numbers on paper to get your bearings (all of these numbers have big error bars). 

So if we're using heart rate to approximate lactate and the associated physiological impacts of fatigue, why don't we just use lactate? Good question, you article-ruining jerk. In a perfect world, athletes may decide to prick themselves for blood lactate readings with every interval like they're Norwegian vampires. Practically, though, there's a lactate learning curve in the best of times that can lead to inaccurate data, and in the worst of times it can take some of the spontaneous artistry out of daily training. You can probably tell I'm scared of blood, needles, and vampires (whether traditional or sexy). 

But have blood-free hope! Using the method in the article, I have approximated zones for professional athletes that have later been validated in lab tests with small enough margins of error to be useful. However, it's key to get a full lab test for truly accurate data. Heart rate without lactate, metabolic, and/or ventilatory lab tests is like determining the time from where the sun is in the sky. With context clues, you can be close, but you wouldn't want to use it to cook a turkey.

Five-Zone Training Model

Now, let's finally get to the Five-Zone heart rate model that is used in most training approaches. The Three-Zone model is overlaid with green, yellow, and red (again, there is debate around the exact breakdown, particularly with the Zone three/Zone four delineation).

There are a few ways to set the zones, but I see the most repeatability and accuracy with the Lactate Threshold Heart Rate method pioneered by legendary coach Joe Friel. As outlined in Training Peaks, he suggests that athletes "do a 30-minute time trial all by yourself (no training partners and not in a race). Again, it should be done as if it was a race for the entire 30 minutes. But at 10 minutes into the test, click the lap button on your heart rate monitor. When done, look to see what your average heart rate was for the last 20 minutes." 

I like athletes to do the test on uphills, where they won't be limited by neuromuscular and biomechanical factors if they don't have a ton of speed training. If it wasn't a truly hard effort or your heart rate takes a lot of time to increase across an effort, you can take the average heart rate from a section as short as 10 minutes. Because this isn't an exact measurement like in a lab test, think of it as an art that is useful in understanding your body, rather than attempting to find a correct answer like high school algebra.

For an easy way to scrub complex data files with HR variation, you can use the Strava Sauce browser plug-in, highlight the area you want to examine, and it will give averages without ever lapping the watch. When I calculate zones for athletes, I have found that you can also approximate LTHR from almost any hard workout with intervals 3 minutes or over by looking for spots in the file where heart rate stabilizes for 15-30 seconds before rising to less sustainable levels (and sometimes falling back toward that baseline in longer efforts). Be careful about using data from very hot days or long races over 90 minutes, when heart rate can sometimes be sustained above Friel's LTHR in ways that are not mirrored by the underlying physiology. 

A big key here: the data needs to be accurate. Chest-straps are ideal for these purposes, and if you are doing a workout to set heart rate zones, it's worth using the chest strap even if it feels like you're getting the heimlich maneuver from a weak octopus. While wrist-straps are rapidly improving in accuracy, there is extreme variation among athletes/watch brands. For example, my Garmin 745 seems to work really well in most circumstances (see this beautiful graph of a threshold workout). But other athletes don't have that success, and sometimes they send me heart rate files that look like Bitcoin price graphs (we are not sure why it's going up and down, but we can be pretty sure it's nefarious). 

How to Set Your Heart Rate Zones

Once you have the LTHR number, it's time to set those elusive zones. We're at another controversial point where the exact percentages are subject to extreme debate. The problem: when you validate heart rate data with lab tests, individual physiology varies substantially. LTHR narrows down that physiological variation to get an idea of zones, but the exact delineation depends on training history, muscle fiber typology, metabolic context, astrological sign, etc. Don't even get me started on Scorpios.

Here are the percentages that Megan and I like to use:

Let's dig into an example from my data. In February, I did a virtual bike race up a mountain. Using the Strava Sauce plug-in and highlighting the final 20 minutes of that hard effort, my LTHR was 172. While there is variance across sports and my heart rate is higher with running, that means my current zones for biking are approximately:

Your LTHR may increase with training and it will drop with age. Athletes are often between 165 and 175, though in professional athletes, I have seen numbers as high as 189 and as low as 152. You can see why dialing in your unique physiology is so important. An athlete with an LTHR of 160 needs to cap most of their easy runs at 140 heart rate (top end of Zone 2). Meanwhile, an athlete with an LTHR of 180 can go all the way up to 157! Often, everything about those athletes can look the same from the outside-same age, same PRs, same training, same potential. But they have very different hearts.

How To Use Your Heart Rate Zones

There are two places where having a general feel for your personal heart rate zones can be most helpful: understanding your Zone 2 (with LT1 as a cap) and determining the sustainability of longer efforts. First, let's break down how to think about each of the zones:

Knowing that Zone two cutoff can help calibrate an athlete's effort so they understand what terms like "easy," "steady," and "moderate" actually mean. Spot-checking heart rate periodically on harder efforts can ensure that athletes aren't going too hard, pushing everything into Zone five and reducing aerobic adaptations. I love athletes to get a feel for how high their heart rate gets on uphills especially, since excessive effort on ups can lead to reduced endurance and race performance. Zone 3 is your friend, in moderation. Zone four is your acquaintance. And spending too much time with Zone five will end with you folded up in a car trunk somewhere outside Las Vegas.

Takeaway

The big takeaway is that heart rate is just a proxy for fatigue processes, especially when calculated outside of a lab. The numbers can vary by the day, and they change across training blocks. Temperature, stress, caffeine, and political news all impact the numbers enough that caring too much about a few beats per minute is unhelpful. The day I first heard the nickname "Meatball Ron," I was in Zone three while sitting on the couch.

Instead, view heart rate as a way to calibrate your physiology in a general way, spot-checking your perceived exertion so that you know what you think your body is doing generally aligns with what your body is actually doing. Once an athlete dials in heart rate, I like them to look at it once every couple weeks during a run, and solely after-the-fact on other runs (if at all), never investing too much in small changes. Heart rate sometimes takes a while to respond, so I find it's rarely useful on shorter intervals.

If you train within the correct general range of intensities, whether guided by heart rate, lactate, and/or perceived exertion, you can improve output at Zone two and Zone three heart rates in particular, and because those efforts are more sustainable metabolically, you'll excel in races. You definitely don't need to have a heart rate monitor to achieve those goals. But you do need to have a good feel for your unique physiology. 

All of our bodies can be well-calibrated wonderlands. We sometimes just need a little bit of the sexiest thing of all: data.

Ethiopia’s Fotyеn Tesfay Haylu delivered one of the most remarkable women’s half-marathon performances ever seen on American soil on Sunday, powering to a commanding victory at the 2026 Buenos Aires Half Marathon in Argentina in 1:03:57.

Running with exceptional confidence and strength, Tesfay took control of the race and produced a superb solo performance to rewrite the event record. Her breathtaking run also carried historic significance, as she became the first woman to break the 64-minute barrier for the half marathon in the Americas, producing what is being celebrated as the fastest women’s half-marathon performance ever recorded on the continent.

The Ethiopian star was in a class of her own, crossing the finish line more than a minute clear of Turkey’s Nevin Can, who finished second in 1:05:06. Another Turkish athlete, Selin Can, completed the podium in third place with 1:05:11, as the leading trio all produced strong performances on the fast streets of Buenos Aires.

Kenya also featured prominently in the top positions, with Irene Jepchumba Kimais taking fourth in 1:06:04, followed by Sheila Chepkirui in fifth with 1:06:13. Magaret Akidor Ngathike finished sixth in 1:06:46, while fellow Kenyan Deborah Samum claimed seventh place in 1:08:32.

Brazil’s Nubia de Oliveira Silva was eighth in 1:11:13, while Argentina’s Sofia Luna and Dahyana Juarez rounded out the top 10 with times of 1:11:21 and 1:11:28, respectively.

Top 10 Women – 2026 Buenos Aires Half Marathon

1. Fotyеn Tesfay Haylu (Ethiopia) – 1:03:57

2. Nevin Can (Turkey) – 1:05:06

3. Selin Can (Turkey) – 1:05:11

4. Irene Jepchumba Kimais (Kenya) – 1:06:04

5. Sheila Chepkirui (Kenya) – 1:06:13

6. Magaret Akidor Ngathike (Kenya) – 1:06:46

7. Deborah Samum (Kenya) – 1:08:32

8. Nubia de Oliveira Silva (Brazil) – 1:11:13

9. Sofia Luna (Argentina) – 1:11:21

10. Dahyana Juarez (Argentina) – 1:11:28

For Tesfay, it was far more than a race victory. Her 1:03:57 performance was a statement of extraordinary quality, combining speed, endurance and remarkable solo running to produce a landmark result in Buenos Aires. In a race that will be remembered for years to come, the Ethiopian did not simply win—she redefined what was thought possible for women’s half-marathon running in the Americas.

Ethiopia’s Yomif Kejelcha produced one of the most extraordinary performances in road racing history on the streets of Buenos Aires, Argentina, reclaiming the half marathon world record with a sensational 56:51 performance at the 2026 Buenos Aires Half Marathon.

The former world record-holder delivered a breathtaking exhibition of speed and endurance to take 29 seconds off the previous pending mark of 57:20, set by Uganda’s Jacob Kiplimo and takes a huge chunk from his own former official world record. Kejelcha's new performance is pending the standard ratification procedures, but if officially ratified, it will return the world record to the Ethiopian star and mark another remarkable chapter in the evolution of the event. 

Kejelcha's achievement is particularly significant because the 57-minute barrier had already been broken before. Jacob Kiplimo had previously run under 57 minutes, clocking 56:42 that was not ratified demonstrating that the once-unthinkable barrier was possible. Kejelcha, however, has become the second man to run under 57-minute barrier who now returns to the top of the all-time rankings with another historic performance in Buenos Aires.

The Ethiopian's race was remarkable not only for the final time but also for the way he built his performance. He covered the opening five kilometres in 13:44 before reaching 10km in 27:18. Rather than slowing, Kejelcha accelerated through the middle stages, passing 15km in 40:39 and 20km in 54:02 as he continued to push the limits of elite road racing.

By the time he reached the finish line, Kejelcha had completed the race at an extraordinary average pace of approximately 2:42 per kilometre, producing one of the most astonishing sustained efforts ever witnessed in distance running. His stunning run sent a powerful message to the athletics world and further strengthened his status as one of the most formidable distance runners of his generation.

Behind the record-breaking champion, Ethiopia completed a dominant clean sweep of the men's podium. Tadese Worku Gebresilase claimed second place in 59:18, while Bereket Nega Batebo secured third in 1:00:17, giving Ethiopia a memorable one-two-three finish in the Argentine capital.

Kenya’s Jonathan Kipkoech Kamosong finished fourth in 1:00:20, followed by compatriot Simon Maywa in fifth with 1:00:55. Argentina’s Ignacio Erario gave the home supporters plenty to celebrate with an impressive sixth-place finish in 1:00:57, breaking the one-hour barrier in front of an enthusiastic local crowd.

Dillon Kipyeko of Kenya finished seventh in 1:01:07, with Robert Kiprop Koech eighth in 1:02:01. Mexico’s Julio Ortiz Ponce took ninth place in 1:03:17, while Colombia’s Jimmy Gómez completed the top 10 in 1:03:34.

The Buenos Aires Half Marathon will now take its place in the history books as the scene of a truly extraordinary breakthrough. For Kejelcha, this was more than just another victory. It was a spectacular return to the top, reclaiming a world record he had previously held and once again rewriting the limits of the half marathon.

The 56:51 performance remains pending ratification, but Yomif Kejelcha's run has already delivered one of the defining moments in the history of road racing.

Kenya delivered another commanding display of distance-running excellence at the Antrim Coast Half Marathon, with Isaia Lasoi leading a memorable Kenyan clean sweep of the men's podium in a race packed with world-class performances.

Lasoi emerged victorious after a thrilling battle at the front, crossing the finish line in a superb 58:26 setting a new course record. His winning performance underlined his strength and speed over the half-marathon distance, but he was made to work all the way by fellow Kenyan Daniel Mateiko, who finished just three seconds behind in 58:29 after an electrifying duel for the title.

The contest between the two leaders produced one of the standout moments of the race, with both athletes pushing deep into elite territory as they fought for victory. In the end, Lasoi found just enough to secure the win, while Mateiko's narrow defeat highlighted the remarkable depth and quality of Kenya's leading distance runners.

Vincent Kipkorir completed the Kenyan sweep, taking third place in 1:00:38 to ensure that all three places on the podium belonged to Kenyan athletes. Samwel Chebolei added further Kenyan strength to the results, finishing fourth in 1:01:01, while Amos Langat was also among the leading finishers.

The international field featured several prominent names. Australia's Jimmy Whelan produced a strong run, while Ethiopia's Yismaw Dillu featured among the front group. American marathon star Galen Rupp also delivered a notable performance, clocking 1:01:29 in another competitive outing for the experienced distance runner. Former world-class track and road athlete Edward Cheserek was also among the top finishers.

Lasoi's 58:26 victory, however, was the defining performance of the day. Together with Mateiko and Kipkorir, he gave Kenya a perfect podium and another emphatic reminder of the country's extraordinary strength in elite road running.

The Antrim Coast Half Marathon once again provided a fast, competitive stage for some of the world's finest distance runners, but when the decisive moments arrived, it was Kenya that owned the podium.

One of the most iconic milestones in the history of ultramarathon running is drawing closer, with entries for the historic 100th edition of the Comrades Marathon set to open on Tuesday, 25 August 2026.

The Comrades Marathon Association has officially announced a detailed entry process for the 2027 race, which will unfold in three stages and give runners around the world the opportunity to secure their place in what promises to be one of the most significant editions ever held of The Ultimate Human Race.

The announcement followed the official launch of the 2027 Comrades Marathon on Wednesday, 19 August, when the centenary campaign, “The Greatest Story Ever Run,” was unveiled alongside a special logo created exclusively for the landmark 100th edition.

The launch also revealed several major highlights for the Centenary Race. The historic event will take place on Sunday, 13 June 2027, and will be a Down Run, with 28,000 places available. The entry process will include a ballot, while the race will offer a record R8.919 million in prize money. Organisers have also set an ambitious goal of raising R10 million for the Amabeadibeadi charities, adding an important charitable dimension to the centenary celebrations. One of the defining moments of the launch was the unveiling of the special Centenary mark, created to commemorate this extraordinary milestone in the history of the race.

The entry process begins on 25 August at 10:00 a.m. SAST, when entries open for Green Number runners, Yellow Number runners and Amabeadibeadi charity entrants.

The next phase follows on 2 September at 10:00 a.m. SAST, when entries open for Comrades Marathon Association members. This window will remain open for 72 hours or until the available entry allocation is filled, with places offered on a strictly first-come, first-served basis.

For general entrants, the process will move to a ballot system. General entries open on 9 September at 10:00 a.m. SAST, with runners able to enter the ballot until it closes on 22 September at 4:30 p.m. SAST. The ballot draw is then scheduled to take place on 23 September.

Several other crucial dates will shape the road to the historic race. The substitution period will run from 15 to 31 March 2027, while 3 May 2027 is the final deadline for runners to submit their qualifying performances, seeding information and other required entry details.

To qualify for the 2027 Comrades Marathon, runners must complete a 42.2km marathon in under five hours between 15 June 2026 and 3 May 2027.

The journey will finally culminate on Sunday, 13 June 2027, when thousands of runners are expected to line up for the historic 100th edition of the Comrades Marathon.

The 2027 race will represent a remarkable moment for the legendary South African ultramarathon. For more than a century, the Comrades Marathon has captured the imagination of runners and spectators with its extraordinary test of endurance, determination and human spirit. Its centenary edition will celebrate the generations of athletes who have faced its demanding roads, conquered its challenges and helped build one of the world's most respected endurance events.

For runners dreaming of becoming part of this historic occasion, the road to Comrades 2027 is now clearly marked. From the opening of entries in August 2026 to race day in June 2027, every deadline will matter.

The Greatest Story Ever Run is preparing for its most historic chapter yet.

American sprint standout Sam Blaskowski is taking steps toward an international future with Poland after uncovering a powerful connection to his family's ancestral homeland.

The 23-year-old sprinter, who has established himself as one of the fastest Americans of his generation with a personal best of 9.89 seconds in the 100 metres, has begun the process of obtaining Polish citizenship with the aim of eventually representing Poland in international competition.

Blaskowski's connection to the country traces back through his great-grandparents, Franciszek and Julian Błaszkowski, who emigrated from Poland to the United States in 1905. Their journey more than a century ago has now opened an unexpected new chapter for their descendant, whose athletic ambitions could soon carry the Błaszkowski name back onto the international stage under Polish colours.

The sprinter has already received support from the Polish Athletics Association as he works through the citizenship and eligibility process. Should his transfer of allegiance be completed, Blaskowski could become a significant addition to Poland's sprint programme.

His credentials certainly make the prospect an exciting one. In addition to his sub-10-second speed over 100 metres, Blaskowski owns a personal best of 19.93 seconds in the 200 metres, demonstrating the kind of versatility that could prove valuable both individually and in Poland's 4x100m relay squad.

For Blaskowski, however, the move is about more than simply changing national colours. It represents an opportunity to reconnect with his family's heritage while pursuing his ambitions at the highest level of the sport.

With his sights set on becoming part of Poland's international sprint team and competing for relay medals, Blaskowski's journey from discovering his Polish roots to potentially representing the country of his ancestors could become one of the most fascinating allegiance stories in world athletics.

A century after Franciszek and Julian Błaszkowski left Poland for America, their family's story may now be coming full circle—this time at full sprint.